This invention relates to a level sensing device for household appliances or the like and comprises a member having a compartment which, at its lower part, via a combined inlet and outlet is connected to a treatment chamber to which liquid is supplied. The upper part of the compartment forms a closed section that is in communication with a pressure sensing means.
It is known in the art to use level sensing devices for household appliances such as dish-washers and washing machines since it is necessary to cut off the supply of water to the machine when the water has reached a predetermined level in the treatment chamber. A common method of sensing the level of water in the treatment chamber is to create a means of communication between the treatment chamber and the lower part of an hermetically sealed compartment by means of a hose while connecting the upper part of the sealed compartment with a pressure sensor. Because of the increase in air pressure in the compartment when water flows into it, the water level in the compartment does not rise as much as the water level in the treatment chamber. When emptying the machine by discharging the water in the treatment chamber, the water which has been collected in the compartment flows into the treatment chamber due to gravity and the pressure built up in the compartment. However, the flow of water from the sealed compartment into the treatment chamber takes a rather long time since air has to flow in the opposite direction of the discharging water. Also, there is a risk that the compartment will not be completely emptied of water due to air leakage, causing the system to work improperly.
GB 1.081.082 shows another type of level sensor for a washing machine wherein the level sensor comprises a container having several sections separated by partition walls. One of the sections is connected to a pressure sensor. A second section is in communication with the other sections by means of a communicating channel and is also connected to a pump by means of a hose. The remaining sections communicate with atmosphere. There also is an overflow device and combined inlet and outlet for water. The purpose of this arrangement is to prevent foam from rising up into the pressure sensing section. However, this device is complicated because of the large number of sections and the separate pump connection required to empty the device.